An offshore plant refers to production facilities that can collect marine resources (crude oil, gas, etc.) or produce target products using marine resources on or under the sea.
Generally, the majority of offshore plants are various types of marine facilities that are used to collect, produce and transport crude oil and natural gas. Recently, competition for the acquisition of subsea resources has been accelerated due to the depletion of onshore and inshore fossil fuel. A field that requires the highest technical capability among offshore plant industries is the field of subsea production and processing systems that process and produce crude oil, gas, etc. in subsea areas. For this reason, subsea production and processing systems have proved themselves to correspond to a higher value-added business.
In offshore plants including undersea plants, multi-phase flows formed of a combination of liquid, gas and solid phases are present in a process of transporting gas or oil as well as a process of producing gas or oil. That is, crude oil, gas, water, sand, mud, etc. located on the seabed are transported through the horizontal/vertical pipes of offshore plants. Such a multi-phase flowing fluid does not support smooth flow. In particular, at a specific pressure and temperature, gas and water are combined into a gas hydrate and thus cause plugging or blocking in a pipe, thereby resulting in a problem with the operation of an offshore plant.
Furthermore, multiple components are present even in the case of a single phase. For example, in a natural gas phase, multiple components, including methane, ethane and propane, are included. These components also considerably influence the flow and characteristics of a fluid.
In practice, when a problem with the flow of a multi-phase flowing fluid occurs in connection with the construction and operation of a floating offshore plant, it is difficult to determine the cause of the problem, the production rate decreases, and enormous expenses are required for recovery.
Accordingly, recently, research into the achievement of flow assurance through the analysis of the characteristics of a multi-phase flowing fluid and the detection of a pipe plugging problem in advance in processes of producing subsea resources and transporting the subsea resources to a marine platform has attracted a lot of attention. As part of the research, an apparatus in which a pipe arrangement capable of simulating an undersea environment in which multi-phase flow was performed was installed on the ground was proposed, and is referred to as a flow loop.
Actually, flow loops were installed and are being operated at the University of Tulsa in the U.S., SwRI in the U.S., IFP in France, SINTEF in Norway, and CSIRO in Australia.
Conventional flow loops or actual offshore plant facilities still remain at a level at which fluid characteristics, such as the pressure, temperature and flow rate of a multi-phase flowing fluid, are measured using measuring instruments and the formation of plugging or blocking attributable to the formation of a gas hydrate is visually observed via a monitoring window.
Meanwhile, even when an administrator is observing the inside of a pipe through the monitoring window at the time at which a hydrate starts to be generated within the pipe, it is nearly impossible to distinguish an initial hydrate and a simple particle from each other with the naked eye, and the time at which a plugging or blocking phenomenon can be dealt with can be considered to have been passed already if the hydrate has been so generated that they can be distinguished from each other.
In practice, when a plugging or blocking phenomenon has already occurred, a corresponding pipeline has been cut away conventionally. Although a reserve pipeline is installed in order to prepare for the cutting away of a pipeline, this cannot be considered to be a fundamental solution.
Currently, there is no method capable of detecting hydrate plugging in advance in a conventional flow loop apparatus or an offshore plant pipeline arrangement. The characteristics (temperature, pressure, and flow rate) of a multi-phase flowing fluid can be immediately measured, but a method of analyzing the composition of a multi-component fluid in real time is not present. For example, shorter-chain hydrocarbons composed of methane CH4, ethane C2H6 and propane C3H8 are main components of natural gas, and longer-chain hydrocarbons (C6H14, C7H16, C8H18, etc.) are in a liquefied form and correspond to components of crude oil. In order to analyze these various components, a chromatography method (a gas or liquid chromatography method) of collecting a sample, separating each component from an analysis column and performing qualitative/quantitative analysis via various detectors (an FID, a TCD, and an MS) is generally best. However, these methods have critical disadvantages in that analysis is difficult to achieve, a measured sample must be discarded because the sample must be collected, and real-time analysis is impossible and also an excessively long analysis time is required because each component must be separated from a column and then analyzed by a detector. That is, it is impossible to individually and rapidly analyze various components in subsea offshore plant facilities or a flow loop using the existing conventional analysis method.